Ionization current

Experimental. The mass spectra in Figures 1-8 are positive-ion spectra produced by electron impact and were obtained from a single-focusing, magnetic deflection Atlas CH4 Mass Spectrometer. The ionizing potential was 70 e.v. and the ionizing current 18/a a. An enamel reservoir heated to 120°C. was used from which the sample was leaked into the ion source. 

Representative mass spectral conditions (negative chemical ionization) ion source temperature, 150°C ionizing current, 0.20 mamp electron energy, 70 eV methane reagent gas (source pressure 0.5 to 1 torr). 

From equations (1) and (4), it is clear that the results of calibration agreed with the theoretical calculation within 8.4 percent. Finally, we have used the experimental results for the relationship between radon concentration and ionization current. 

Tachino, T., Y. Ikebe and M. Shimo, Wall Effect of Ionization Chambers in Measurement of Ionization Current due to Several Gaseous... 

Ionization in the condensed phase presents a challenge due to the lack of a precise operational definition. Only in very few cases, such as the liquefied rare gases (LRG), where saturation ionization current can be obtained at relatively low fields, can a gas-phase definition be applied and a W value obtained (Takahashi et al., 1974 Thomas and Imel, 1987 Aprile et al., 1993). 

Another method is the indirect measurement of gas concentrations in a mixture To detect a flame in household gas appliances it is usual to record the ionization current, which reveals more than just the existence of a flame. The junction between the ionization of a reacting gas and the stoichiometric value 7 of this combustion is one very promising possibility of controlling the combustion [8]. 

As indicated in Fig. 3.21, the ionization current shows a maximum near the stoichiometric level of combustion. By introducing a set point for the ionization current the excess air can be adjusted in order to achieve optimum combustion conditions. 

Apart from the primary air ratio, the ionization current depends on various other factors, such as differences in heat load, fuel gas composition, voltage supply of the probe, design of the burner, the position of the electrodes and also different temperatures of solids in the combustion chamber. All these disturbing fac-... 

In a comprehensive test program the characteristic functions of the ionization current and the primary air ratio as well as of the primary air ratio and the fan supply voltage have been gathered. A closed loop control has been designed on this basis, which also includes appliance start-up and calibration as well as a suitable, dynamic set point and actuator controls. 

Another low-cost alternative method is to measure parameters which can indirectly provide information about the combustion quality, such as the ionization current in the burner flame ( SCOT method). 

In order to measure the absorption of the beam of rays coming from the mercury vapor an ionization chamber with a thin mica window in it and containing methyliodide was set up opposite the window, F, and lead plates with holes in them were placed in the line of the beam so that only the radiation coming from the impacts of the electrons against the mercury entered the chamber with sufficient intensity to be detected. That this was the case in the actual experiments is indicated by the fact that no perceptible ionization current could be observed when the mercury pump was not running. A quadrant electrometer measured the ionization current. 

R. B. Owens. He observed in 1899 that the ionization current through a confined volume of air exposed to the rays from thorium compounds decreased to a minimum when air was drawn through his apparatus. Rutherford showed that this effect is caused by the emission of thorium emanation, now known as thoron. This photograph was taken in about 1910 when Professor Owens was at McGill University. 

Finally, the ionization current per gram, sy, has been calculated for 21 days after the event and compared with s95. Unlike the cloud sample, the KH sample was fractionated. The standardized (i.e., corrected to a reading of 560 X 10"9 ma. for a 100-/xgram radium standard) unfractionated value of this ratio at 21 days has been determined by Mackin to be 4.7 X 10"21 ma. per fission (10). The value determined here is only half of the theoretical value. Crockers calculations show that 140La contributes 60% of the ionization rate from an unfractionated sample at this time (2). Depletion in 140La therefore undoubtedly contributes to the... 

The 02( A) state can be detected by measuring the ionization current (682) produced by light absorption below 1118 A... 

If an ionized gas is left to itself, the ions soon recombine anil become neutral. But if it is subjected to an electric field, as in an ionization chamber, the ions pass to the electrodes, such a migration being an ionization current, Such currents, commonly called electric discharges, ate attended by diverse phenomena and vary widely in character from the silent glow discharge to the lightning stroke. 

Fig. 7.4 Na 18s ionization threshold. The field ionization current is plotted vs the peak...

When a compound absorbs the energy of a photon of light it becomes ionized and gives up an electron. This is the basis for the photoionization detector (PID). The capillary column effluent passes into a chamber containing an ultraviolet (UV) lamp and a pair of electrodes. As the UV lamp ionizes the compound, the ionization current is measured. 

Table I contains our new values for the L2 and Ls absorption limits of Pt, Au and Bi. These measurements were taken with almost the same arrangement of apparatus as before. The X-ray tube was provided with an arm which reached nearly to the first slit of the spectrometer, thus reducing the absorption of X-rays by air. At the end of this arm and also on the front of the ionization chamber thin mica windows were employed which still further reduced the absorption of X-radiation. Finally the sensitivity of our electrometer had been increased many times. We were thus supplied with a much more sensitive detector of X-ray spectra than in our earlier measurements. This enabled us to use narrower slits and to obtain at the same time greater drops in our ionization currents for the absorption limits.

Significant Mass Spectrometry operational parameters were as follows ionization voltage, 70 eV ionization current, 200ifA source temperature, 200°C electron multiplier voltage, 1.9 kV integration time, 1 ms/a.m.u.. For optimum sample transfer, a transfer temperature of 200°C was employed. 

---